A magnetic storage device typically comprises one or more magnetic disks, each having at least one data recording surface including a plurality of concentric tracks of magnetically stored data, means such as a spindle motor and spindle motor controller for supporting and rotating the disk(s) at a selected RPM, at least one read/write transducer or "head" per recording surface formed on a liquid bearing slider for reading information from and writing information to the recording surface, a data channel for processing the data read/written, a positionable actuator assembly for supporting the transducer in close proximity to a desired data track, and a servo system for controlling movement of the actuator assembly to position the transducer(s) over desired ones of the tracks.
Each slider is attached on one surface to an actuator arm via a flexible suspension and includes on an opposite side a liquid bearing surface (LBS) of a desired configuration to provide favorable fly height characteristics. In contact recording disk drive designs, the slider and transducer are in continuous contact with the storage disk, which may be coated with a lubricant to reduce wear on the slider. In contact start/stop disk drive designs, the slider and transducer are only in contact with the recording surface when the spindle motor is powered down. As the disk begins to rotate, an airflow is generated which enters the slider's leading edge and flows in the direction of its trailing edge. The airflow generates a positive pressure on the LBS, also called an air bearing surface or ABS, lifting the slider above the recording surface. As the spindle motor reaches operating RPM, the slider is maintained at a nominal fly height over the recording surface by a cushion of air. Then at spin-down, fly height drops until the slider is once again in contact with the disk.
Because contact start-stop recording subjects the slider and transducer to extensive wear, some disk drive designs alternatively employ "load/unload" technology. According to this design, a ramp is provided for each slider/suspension assembly at the inner or outer diameter of the disk where the slider is "parked" securely while the spindle motor is powered down. During normal operation, the disk speed is allowed to reach a selected RPM (which may be below the normal operating RPM) before the head is "loaded" onto the disk from the ramp on the liquid or the air cushion generated by the disk's rotation. In this manner, the slider flies over the disk without significant contact with the disk surface, reducing contact start-stop wear substantially.
The sensitivity of the transducer to information in the storage surface increases with decreasing slider fly height. Thus information may be recorded at higher bit and track densities on the recording surface if the fly height of the slider can be maintained in close proximity to the disk. But lower flying altitudes subject the slider ABS to the accumulation of debris which may become lodged in the transducer read and write gaps, impairing data transfer. Debris may be introduced to the disk surface during the manufacture or assembly of the disk drive, from moving parts that wear over a period of time, a faulty air filtering system, or slider contact with disk asperities, for example. The debris may also accumulate along the air bearing surface features, degrading fly height performance. Fly height degradation may be in the form of increased fly height leading to signal loss, or a decrease in fly height leading to "head crash", i.e., impact with the disk. Head/disk impact can cause severe damage to the transducer, slider, and disk coating, resulting in unrecoverable data.
It is therefore desirable to periodically remove head debris. In contact start-stop designs, debris removal is accomplished when the head comes into physical contact with the disk surface. As the slider in contact with the disk, the accumulated debris is scraped off by the disk surface. In load/unload designs, such cleaning is not possible, since the head preferably never comes into contact with the disk.
U.S. Pat. No. 5,486,970 to Lee et al., is directed to a head cleaning apparatus mounted adjacent to a disk comprising a base, a ratchet, and a cleaning pad with bristles rotated by the ratchet in a plane parallel to the plane of the disk. The head is loaded onto the cleaning pad by a ramp, and is cleaned by the rotating bristles. The design is undesirable for small disk drive designs with limited space at the disk perimeter, since sufficient space must be provided to accommodate the rotating mechanism.
What is needed, therefore, is a space-efficient ramp structure and method for removing debris from a slider during the load/unload process so reading, writing, and fly height performance are not adversely affected.